Radially expanding implants

ABSTRACT

Orthopedic implants being at least in part radially expandable at one of the leading or trailing ends to expand both the height and at least a portion of the width of the implant, and instruments and methods for inserting the implants into an implantation space are disclosed.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/105,839,filed Mar. 25, 2002 now U.S. Pat. No. 7,128,760; which claims benefit ofprovisional Application No. 60/279,205, filed Mar. 27, 2001; andprovisional Application No. 60/281,714, filed Apr. 4, 2001; all of whichare incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to interbody spinal implants,and instruments and methods for inserting interbody spinal implants intoan implantation space in the spine, and in particular to an expandableinterbody (for placement at least in part between adjacent vertebralbodies in the space previously occupied by disc material) spinal fusionimplants for the immobilization of adjacent vertebrae.

2. Description of the Related Art

Expandable spinal fusion implants have height raising capabilities thatare utilized once the implant is initially positioned. Such heightraising capability may be utilized within the spine anteriorly,posteriorly, or both and to various extents, respectively to raise thefront or back of the implant. More particularly, such implants haveupper and lower surfaces of upper and lower portions that in aninsertion position are collapsed relative to one another and in adeployed position are spaced further away from one another than in thecollapsed position.

Expandable fusion implants offer the advantage of allowing for theplacement of a potentially larger implant through a smaller opening in apatient's body. The first expandable spinal fusion (allowing for thegrowth of bone from vertebral body to vertebral body through theimplant) implant was invented by Michelson and also is disclosed in U.S.Pat. No. 5,776,199, filed Jun. 28, 1988, which is hereby incorporated byreference herein.

Expandable interbody spinal fusion implants preferably may be insertedfrom an anterior approach to the spine, an approach posterior to thevertebral transverse processes, or to either side of the spinal midlinein pairs. Such expandable implants are adapted to increase in height attheir leading ends or at their trailing ends from a collapsed state toan expanded state for the purpose of increasing spinal lordosis at thatinterspace. During installation of expandable interbody spinal fusionimplants, it is desirable that the surgeon have the ability to preciselycontrol the implant with the appropriate instruments and methods to loadthe implant with appropriate bone growth promoting material, to insertthe implant into the implantation space, to deploy the implant to afinal expanded state, and to further load the implant with bone growthmaterial if so desired.

Also known in the art are expandable interbody spinal fusion implantsthat are circumferentially expandable at one of their leading ortrailing ends to expand both the height and the width of the implant.Such implants have an expansion mechanism that is moved from thetrailing end through the interior of the implant to reach the leadingend to expand the implant. Any bone growth material present within theinterior of the implant would be forced out of the interior of theimplant by the expansion mechanism passing therethrough. Accordingly,such implants cannot be effectively preloaded with bone growth promotingmaterial prior to expansion of the implant.

There exists a need for a circumferentially expanding implant that issubstantially hollow and substantially devoid of any elaborate orsubstantial space occupying expansion mechanism to permit preloading ofthe implant with bone growth promoting material prior to expansion ofthe implant. The expansion mechanism would not interfere with thecapacity to compressively load osteogenic material such as bone or anyother suitable material through the length of the implant and to have itextrude from the implant. The extrusion of the osteogenic material fromthe implant provides an increased volume of osteogenic material over agreater surface area of the adjacent vertebral bodies adjacent the discspace to be fused and beyond the surface area of contact of the implantto the vertebral bodies themselves. Surrounding the implant itself withadditional fusion promoting substances in contact with the adjacentvertebral bodies may enhance the fusion process.

There also exists a need for instruments and methods for use withexpandable interbody spinal fusion implants providing for all of theaforementioned needs individually or in combination.

SUMMARY OF THE INVENTION

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

The present invention is directed to an interbody spinal fusion implantparticularly adapted for anterior, posterior, and posterior lateralinterbody spinal fusion; and methods and instrumentation for a preferredinsertion of these implants.

The present invention implant is adapted to have a generally constantsize at one end while allowing for a generally circumferential increasein size at the opposite end. This feature is particularly useful forposterior lumbar interbody fusion and posterior lateral interbody spinalfusion, where it is desirable to have the vertebral bodies spaced apartmore anteriorly than posteriorly to restore the lumbar lordosis. Theimplant is preferably inserted in a generally cylindrical form or moreparticularly with the opposed surfaces of the implant adapted to contacteach of the opposed adjacent vertebral bodies adjacent to the disc spaceto be fused being generally parallel. Subsequently, the implant isexpanded at the leading end so that the opposed vertebral body engagingsurfaces of the implant are then in a generally angular relationship toeach other over a substantial portion of the length of the implants. Thepresent invention methods and instrumentation in conjunction with thepresent invention implant allows for the installation of an implant thatin its final implanted form is substantially hollow with the exceptionof an expander ring which is itself preferably hollow so as to notinterfere with the full loading of the implant and the extrusion therethrough of the selected osteogenic material.

In accordance with the purposes of the present invention, as embodiedand broadly described herein, an interbody spinal fusion implant isprovided for implantation from at least in part a posterior approach atleast in part within and across the height of a disc space between twoadjacent vertebral bodies of an adult human spine. The implant includesa body having a leading end for insertion first into the disc space, atrailing end opposite the leading end, and a mid-longitudinal axis alongthe length of the body. The body has an upper portion adapted to contactone of the adjacent vertebral bodies, a lower portion opposite the upperportion adapted to contact another one of the adjacent vertebral bodies,and at least one side portion between the upper and lower portions. Eachof the upper, lower, and side portions extend from the trailing end ofthe body and are spaced apart from one another to form a hollow interiortherebetween. The hollow interior is configured to hold at least somebone growth promoting material therein. The upper and lower portions areconfigured to permit for the growth of bone from adjacent vertebral bodyto adjacent vertebral body through the body of the implant. Each of theupper, lower, and side portions are configured to move at least in partin a direction away from the mid-longitudinal axis of the body to allowfor expansion of the height and at least a portion of the width of thebody. The upper, lower, and side portions have a collapsed positionrelative to one another allowing for a collapsed height and width of thebody, and an expanded position relative to one another allowing for anexpanded height and width of the body. The expanded height and width ofthe body is greater than the collapsed height and width of the body,respectively.

The implant also includes an expander positioned at least in part withinthe hollow interior. The expander is configured to cooperatively engagean instrument adapted to be inserted through the trailing end of thebody to engage and to move the expander from a position proximate theleading end when the body is in the collapsed position away from theleading end toward the trailing end of the body to place the body in theexpanded position. The expander is adapted to contact and to move theupper, lower, and side portions away from the mid-longitudinal axis ofthe body. The upper, lower, and side portions of the body are adapted tocooperatively engage the expander to locate the expander at a locationalong the length of the body between and away from each of the leadingand trailing ends and to resist dislodgment of the expander from thatlocation when the implant is in use. The expander is adapted to hold atleast a portion of the upper, lower, and side portions apart so as tomaintain the expanded height and width of the body and to resist thecollapse of the body to the collapsed body height and width when thebody is in the expanded position.

In accordance with the purposes of a further embodiment of the presentinvention, as embodied and broadly described herein, an interbody spinalfusion implant is provided for implantation from at least in part ananterior approach at least in part within and across the height of adisc space between two adjacent vertebral bodies of an adult humanspine. The body has a base proximate the leading end, an upper portionadapted to contact one of the adjacent vertebral bodies, a lower portionopposite the upper portion adapted to contact another one of theadjacent vertebral bodies, and at least one side portion between theupper and lower portions. Each of the upper, lower, and side portionsextend from the base of the body and are spaced apart from one anotherto form a hollow interior therebetween. Each of the upper, lower, andside portions are configured to move at least in part in a directionaway from the mid-longitudinal axis of the body to allow for expansionof the height and at least a portion of the width of the body. Theupper, lower, and side portions have a collapsed position relative toone another allowing for a collapsed height and width of the body, andan expanded position relative to one another allowing for an expandedheight and width of the body. The expanded height and width of the bodyis greater than the collapsed height and width of the body,respectively.

The implant also includes an expander at least in part within the hollowinterior. The expander is configured to contact an instrument that isadapted to be inserted through the trailing end of the body to move theexpander from a position proximate the trailing end when the body is inthe collapsed position away from the trailing end and toward the base ofthe body to place the body in the expanded position. The expander isadapted to contact and to move the upper, lower, and side portions awayfrom the mid-longitudinal axis of the body. The upper, lower, and sideportions of the body are adapted to cooperatively engage the expander tolocate the expander at a location along the length of the body betweenand away from each of the leading and trailing ends and to resistdislodgment of the expander from that location when the implant is inuse. The expander is adapted to hold at least a portion of the upper,lower, and side portions apart so as to maintain the expanded height andwidth of the body and to resist the collapse of the body to thecollapsed body height and width when the body is in the expandedposition.

In accordance with the purposes of a further embodiment of the presentinvention, as embodied and broadly described herein, a method of thisinvention is provided for inserting an interbody spinal fusion implantfrom at least in part a posterior approach at least in part within andacross the height of a disc space between two adjacent vertebral bodiesof an adult human spine. The method includes providing the spinalimplant having a body with a leading end for insertion first into thedisc space, a trailing end opposite the leading end, a mid-longitudinalaxis, upper and lower portions, and at least one side portion. Each ofthe upper, lower, and side portions extend from the trailing end of thebody. A hollow interior is between the upper and lower portions. Theimplant includes an expander for expanding the height and at least aportion of the width of the body. The method includes preparing animplantation space to receive the implant from a posterior approach tothe spine; inserting the implant at least in part into the implantationspace; and moving the expander from a position proximate the leading endtoward the trailing end of the body along at least a portion of thelength of the body of the implant to move the upper, lower, and sideportions in a direction away from the mid-longitudinal axis of the bodyof the implant to expand the height and at least a portion of the widthof the body of the implant.

In accordance with the purposes of a further embodiment of the presentinvention, as embodied and broadly described herein, a method of thisinvention is provided for inserting an interbody spinal fusion implantfrom at least in part an anterior approach at least in part within andacross the height of a disc space between two adjacent vertebral bodiesof an adult human spine. The method includes providing the spinalimplant having a body with a leading end for insertion first into thedisc space, a trailing end opposite the leading end, a mid-longitudinalaxis, upper and lower portions, and at least one side portion. Each ofthe upper, lower, and side portions extend from the leading end of thebody. A hollow interior is between the upper and lower portions. Theimplant includes an expander for expanding the height and at least aportion of the width of the body. The method includes preparing animplantation space to receive the implant from an anterior approach tothe spine; inserting the implant at least in part into the implantationspace; and moving the expander from a position proximate the trailingend toward the leading end of the body along at least a portion of thelength of the body of the implant to move the upper, lower, and sideportions in a direction away from the mid-longitudinal axis of the bodyof the implant to expand the height and at least a portion of the widthof the body of the implant.

In accordance with the purposes of a further embodiment of the presentinvention, as embodied and broadly described herein, an apparatus isprovided for inserting at least in part within and across the height ofa disc space between two adjacent vertebral bodies of the human spine aspinal implant having upper and lower portions, and an expander forexpanding the height and at least a portion of the width of the implantfrom a collapsed position to an expanded position. The apparatusincludes an inserter guide having a leading end and a trailing end. Theleading end of the inserter guide is configured to cooperatively engagethe trailing end of the implant. The inserter guide has a hollowinterior forming a passage from the trailing end to the leading endthrough the inserter guide. The apparatus also includes a post adaptedto be inserted at least in part through the trailing end of the implantand into a hollow interior of the implant for moving the expander alongat least a portion of the length of the implant between the upper andlower portions of the implant. The post has a leading end configured tocooperatively engage the expander and a trailing end adapted to becoupled to the implant and cooperatively engage an instrument for movingthe post. The apparatus also includes an inner shaft that is configuredto be inserted at least in part within the passage of the inserterguide. The inner shaft has a leading end and a trailing end. The leadingend of the inner shaft is configured to cooperatively engage thetrailing end of the post. The inner shaft is adapted to move the post soas to move the expander toward the trailing end of the implant to expandthe height and at least a portion of the width of the implant.

In accordance with the purposes of a further embodiment of the presentinvention, as embodied and broadly described herein, an apparatus isprovided for use with a spinal implant having an expander for expandingthe height of the implant from a collapsed position to an expandedposition. The implant has a leading end for insertion first into a discspace between two adjacent vertebral bodies of the human spine and atrailing end opposite the leading end. The implant has at least upperand lower portions adapted to be moved away from one another by theexpander when positioned therebetween. The apparatus includes anelongated shaft having a leading end and a trailing end opposite theleading end, and a mid-longitudinal axis. The apparatus also includes anenlarged head proximate the leading end of the shaft that is configuredto be inserted at least in part between the upper and lower portions ofthe implant. The enlarged head is adapted to move apart the upper andlower portions to release the expander therebetween. The apparatus alsoincludes a projection extending from the enlarged head that is adaptedto cooperatively engage the expander for removal of the expander fromwithin the implant.

In accordance with the purposes of a further embodiment of the presentinvention, as embodied and broadly described herein, an apparatus isprovided for inserting at least in part within and across the height ofa disc space between two adjacent vertebral bodies of the human spine aspinal implant having an expander for expanding the height and at leasta portion of the width of the implant from a collapsed position to anexpanded position. The implant has upper, lower, and side portionsincluding a plurality of arms separated by spaces. The apparatusincludes an inserter having a leading end and a trailing end oppositethe leading end. The leading end of the inserter guide has a pluralityof spaced apart portions that are configured to fit in the spacesbetween the arms of the spinal implant to cooperatively engage theinserter to the implant.

In accordance with the purposes of yet a further embodiment of thepresent invention, as embodied and broadly described herein, anapparatus is provided for holding a spinal implant having an expanderfor expanding the height and at least a portion of the width of theimplant from a collapsed position to an expanded position. The implanthas upper, lower, and side portions comprising a plurality of armsseparated by spaces. The apparatus includes a sleeve having a leadingend and a trailing end and a passageway from the trailing end to theleading end. The passageway provides access to the implant through thesleeve. The leading end of the sleeve has a plurality of spaced apartportions that are configured to fit in the spaces between the arms ofthe spinal implant to cooperatively engage the sleeve to the implant.

In accordance with the purposes of a further embodiment of the presentinvention, as embodied and broadly described herein, an apparatus isprovided for use with a spinal implant having an expander for expandingthe height of the implant from a collapsed position to an expandedposition. The implant has a leading end for insertion first into a discspace between two adjacent vertebral bodies of the human spine and atrailing end opposite the leading end. The implant has at least upperand lower portions adapted to be moved away from one another by theexpander when positioned therebetween. The apparatus includes anelongated shaft having a mid-longitudinal axis, a leading end, and atrailing end opposite the leading end. The leading end has a boretherein and an enlarged head with a collar in movable relationship tothe head that permits rotational movement of the head independent of thecollar. The collar and the head are configured to be inserted at leastin part between the upper and lower portions of the implant. The collaris adapted to bear against and move apart the upper and lower portionsof the implant to release the expander therebetween. The apparatus alsoincludes a post that is adapted to be inserted at least in part throughthe trailing end of the spinal implant for guiding the elongated shaftalong the mid-longitudinal axis between the upper and lower portions ofthe implant. The post has a leading end configured to cooperativelyengage the implant and a trailing end that is adapted to be receivedwithin the bore of the elongated shaft. The head of the elongatedshafted is adapted to rotate about the post.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate the embodiments of the inventionand together with the description, serve to explain the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a spinal fusion implant,radial expander of the implant, and threaded post in accordance with apreferred embodiment of the present invention for posterior insertioninto the spine;

FIG. 2 is an assembled trailing end perspective view of the embodimentof FIG. 1;

FIG. 3 is a trailing end elevation view of the embodiment of FIG. 2;

FIG. 4 is a side elevation view of the embodiment of FIG. 2;

FIG. 5 is a leading end elevation view of the embodiment of FIG. 2;

FIG. 6 is a leading end elevation view of a radial expander of theimplant of FIG. 1;

FIG. 7 is a side elevation view of the radial expander of FIG. 6;

FIG. 8A is a trailing end elevation view of the radial expander of FIG.6;

FIG. 8B is a trailing end elevation view of a radial expanderincorporating two alternative embodiments in accordance with the presentinvention;

FIG. 9 is a partial side sectional view of the embodiment of FIG. 2prior to the implant being radially expanded;

FIG. 10 is a partial side sectional view of the embodiment of FIG. 2with the implant in partial radial expansion;

FIG. 11 is a partial side sectional view of the embodiment of FIG. 2with the implant in a radially expanded state;

FIG. 12 is a side elevation view of one embodiment of a driverinstrument for inserting the implant of FIG. 1;

FIG. 13 is a distal end view of the driver instrument of FIG. 12;

FIG. 14 is a perspective proximal end view of the funnel-shaped end ofthe driver instrument of FIG. 12;

FIG. 15 is a side elevation view of one embodiment of a rotatinginstrument used to rotate the threaded post to move the radial expanderto radially expand the implant of FIG. 1;

FIG. 16 is a side elevation view of one embodiment of a plungerinstrument for inserting bone growth promoting material into the implantof FIG. 1 and the disc space;

FIG. 17 is a side elevation view of the plunger instrument of FIG. 16 inan extended state;

FIG. 18 is a perspective view of the posterior aspect of a lumbarsegment of a spine with the dural sac retracted to the left showing apartial discectomy and an expandable guard with disc penetratingextensions approaching the disc space between the adjacent vertebralbodies with the disc penetrating extensions in an insertion position;

FIG. 19 is a side view of the guard of FIG. 18 being inserted within thespine with the disc penetrating extensions parallel to one another inthe insertion position;

FIG. 20 is a side view of the guard of FIG. 18 in the deployed positionwith the disc penetrating extensions shown in an expanded position toinduce angulation of the adjacent vertebral bodies;

FIG. 21 is a side view of the guard of FIG. 18 in the deployed positionwith the disc penetrating extensions in an expanded position to induceangulation of the adjacent vertebral bodies and in partial cross-sectionto show a side view of a drill being inserted through the guard;

FIG. 22 is a side view of the guard of FIG. 18 in partial cross-sectionshowing the spinal fusion implant of FIG. 1 and the driver instrument ofFIG. 12 passing through the guard to install the implant into a preparedimplantation space across the height of the restored disc space and intothe adjacent vertebral bodies;

FIG. 23 is a side view of the implant of FIG. 1 in a non-expanded stateinserted into the implantation space and the rotating instrument of FIG.15 passing through the driver instrument of FIG. 12 and guard of FIG. 18both shown in partial cross section to engage the threaded post;

FIG. 24 is a side view of the implant of FIG. 1 radially expanded in theimplantation space via the rotating instrument of FIG. 15 that passesthrough the driver instrument and guard both shown in partial crosssection;

FIG. 25 is a side view of the rotating instrument of FIG. 15 removingthe threaded post from the implant of FIG. 1 through the driverinstrument and guard both shown in partial cross section;

FIG. 25A is an enlarged fragmentary view along line 25A of FIG. 25showing the cooperative engagement of the driver instrument and threadedpost;

FIG. 26 is a partial side sectional view of the guard and driverinstrument with the plunger instrument of FIG. 16 inserted therein andbeing used to fill the interior of the implant of FIG. 1 with bonegrowth promoting material;

FIG. 27 is a partial side sectional view of the guard and driverinstrument with the instrument of FIG. 16 in an extended state insertedtherein for delivering bone growth promoting material beyond the radialexpander and to regions of the disc space beyond the leading end of theimplant not occupied by the implant;

FIG. 28 is a partial side sectional view of the implant of FIG. 1 in anexpanded state with the threaded post being partially threaded into theradial expander;

FIG. 29 is a partial side sectional view of the implant of FIG. 1 withthe post partially threaded into the radial expander being advancedtoward the leading end of the implant to unseat the radial expander andreturn the implant to the non-expanded state for posterior extraction ofthe implant from the implantation space;

FIG. 30 is a side elevation view of one embodiment of a removerinstrument used to unlock and remove a seated radial expander from ananterior approach and through the leading end of the implant to placethe implant of FIG. 1 into a non-expanded state;

FIG. 31 is a partial side sectional view of the remover instrument ofFIG. 30 being used to expand the implant anteriorly to unlock anddisplace the expander to allow for removal of the implant;

FIG. 32 is a partial side sectional view of the implant shown in FIG. 1in a non-expanded state with the radial expander being removed from theleading end of the implant by the remover instrument of FIG. 30;

FIG. 33 is an exploded perspective view of a spinal fusion implant,radial expander, and threaded post in accordance with another preferredembodiment of the present invention for anterior insertion into thespine;

FIG. 34 is a side elevation view of the embodiment of FIG. 33;

FIG. 35 is a leading end elevation view of the embodiment of FIG. 33;

FIG. 36 is a trailing end elevation view of the embodiment of FIG. 33;

FIG. 37 is a perspective view of an alternative embodiment of theimplant and threaded post of FIG. 33 having two diametrically opposedshortened arms;

FIG. 38 is a perspective view of an alternative embodiment of theimplant of FIG. 33 having arms of generally the same length;

FIG. 39 is a trailing end elevation view of the radial expander of FIG.33;

FIG. 40 is a side elevation view of the radial expander of FIG. 33;

FIG. 41 is a leading end elevation view of the radial expander of FIG.33;

FIG. 42 is a fragmentary side elevation view of the leading end of oneembodiment of a driver instrument for inserting the implant of FIG. 33;

FIG. 43 is a side elevation view of one embodiment of an instrument forholding the implant of FIG. 33 while the radial expander of FIG. 33 isadvanced through the interior of the implant;

FIG. 44 is a fragmentary side elevation view in partial cross section ofone embodiment of a rotating instrument used to linearly advance theradial expander along the threaded post and into the implant to radiallyexpand the implant of FIG. 33;

FIG. 45 is a fragmentary side elevation view in partial cross section ofone embodiment of an instrument for use in removing the post from theimplant of FIG. 33;

FIG. 46 is a side elevation view of two adjacent vertebrae and a hollowguard for use in preparing a disc space to receive the implant of FIG.33;

FIG. 47 is a side elevation view of the adjacent vertebrae and guard ofFIG. 46 in partial cross-section and a side view of a drill beinginserted through the guard;

FIG. 48 is an exploded side view of the implant of FIG. 33, theinstrument of FIG. 42, and an implant receiving space formed across theheight of the disc space and the adjacent vertebral bodies shown inpartial cross section;

FIG. 49 is a side elevation view of the implant of FIG. 33 in anon-expanded state inserted into the implant receiving space formedacross the height of the disc space and two adjacent vertebral bodies incross section and a fragmentary view of the instrument of FIG. 43 inpartial cross section being positioned to engage the arms of the implantwith the instrument of FIG. 44 shown in partial cross section beinginserted therethrough for cooperative engagement with the post;

FIG. 50 is a side elevation view in partial cross section of the implantof FIG. 33 with the instrument of FIG. 44 in rotational engagement withthe post of FIG. 33 moving the radial expander into the implant;

FIG. 51 is a side elevation view in partial cross section of the implantof FIG. 33 with the instrument of FIG. 45 being used to remove the postof FIG. 33 from the implant in the expanded state;

FIG. 52A is a top plan view in partial cross section of a vertebra withtwo implants of FIG. 33 in an expanded state installed side-by-side intoa disc space from an anterior approach with the trailing ends in closeproximity to each other and the shortened arms oriented toward theantero-lateral aspects of the vertebral body;

FIG. 52B is a top plan view in partial cross section of a vertebra withtwo implants of FIG. 33 in an expanded state installed side-by-side intoa disc space from an anterior approach with the trailing ends in closeproximity to each other in a toed-in orientation and the shortened armsoriented toward the antero-lateral aspects of the vertebral body;

FIG. 53 is a fragmentary top plan view in partial cross section of avertebra with two implants of FIG. 37 in an expanded state installedside-by-side into a disc space from an anterior approach with thetrailing ends in closer proximity to each other than in FIG. 52A;

FIG. 54 is a side elevation view of a preferred embodiment of a removerinstrument used to remove an installed radial expander from an implantto collapse the implant of FIG. 33 into a non-expanded state;

FIG. 55 is a partial side sectional view of the implant of FIG. 33 andthe instrument of FIG. 54 being used to unlock the radial expander; and

FIG. 56 is a partial side sectional view of the implant of FIG. 33 withthe instrument of FIG. 54 being fully deployed in the implant and a hookbeing used to extract the radial expander from the implant.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description is intended to be representative only and notlimiting and many variations can be anticipated according to theseteachings, which are included within the scope of this inventiveteaching. Reference will now be made in detail to the preferredembodiments of this invention, examples of which are illustrated in theaccompanying drawings.

FIGS. 1-11 show a preferred embodiment of a radially expandable implantand threaded post used to expand the implant in accordance with thepresent invention. As shown in FIGS. 1-5, implant 100 preferably is aspinal fusion implant adapted to be installed from at least in part aposterior approach to the spine into an implantation space formed acrossthe height of a spinal disc and into two adjacent vertebral bodies.Implant 100 has a body with a trailing end 102, a leading end 104 forinsertion first into the disc space, and preferably has a hollowinterior 103. Leading end 104 is preferably open to permit access tohollow interior 103 of implant 100 through leading end 104. Hollowinterior 103 is preferably configured to hold at least some bone growthpromoting material therein.

Implant 100 includes at least upper and lower arcuate portions 106 a and106 b adapted to be oriented toward and contact adjacent upper and lowervertebral bodies, respectively, and preferably has opposite sides 108 aand 108 b. Arcuate portions 106 a, 106 b and sides 108 a, 108 b includearms 110 that extend from trailing end 102 along at least a part of thelength of the implant toward leading end 104. Arms 110 are preferablyseparated by a space 112. Spaces 112 may be of different lengths andwidths and may, for example, be in the shape of a slit, a slot, or anyother shape suitable for the intended purpose of spacing apart arms 110.Preferably, spaces 112 permit for the growth of bone from adjacentvertebral body to adjacent vertebral body through the body of implant100.

As best shown in FIGS. 9-11, arms 110 have an interior surface 114facing hollow interior 103 of implant 100 configured to bear against andhold a radial expander for forcing apart arms 110 from within hollowinterior 103. Preferably, upper portion 106 a, lower portion 106 b, andat least one of sides 108 a, 108 b are configured to locate an expanderalong the length of the body of implant 100 between and away from eachof trailing and leading ends 102, 104 and to resist dislodgement of theexpander when implant 100 is in use. Interior surface 114 of arms 110 ofat least upper and lower arcuate portions 106 a, 106 b preferably has aramped portion 116 and seat 118 for receiving an expander 120. Each arm110 preferably is of such length, thickness, and material to resistrotational torquing forces during rotation of implant 100 while beingflexible enough to move in a radial direction away from themid-longitudinal axis of implant 100 when forced apart from the interiorof implant 100. For example, one embodiment of implant 100 has six arms110, each of which flexes in a radial direction away from themid-longitudinal axis; thus, each arm 110 moves in a direction differentfrom that of any of the other arms 110 of implant 100. Preferably, eacharm 110 is sufficiently resilient so that each arm 110 may be moved awayfrom the mid-longitudinal axis of implant 100 and may be permitted toreturn to its original orientation if desired without substantialdeformation. Examples of preferred materials for arms 110 include, butare not limited to, metals such as titanium and stainless steel,plastics, and carbon fibers among others. Arms 110 may be engineered tohave a flexibility and springiness optimal for the stiffness of the areaof the spine into which they are to be implanted.

In the expanded position, arms 110 may be at least in part concave alongat least a portion of the length of implant 100. A concave configurationof arms 110 provides a desirable springiness and resilience forcontacting and supporting the vertebral bodies adjacent implant 100.Although it is preferred to have movable arms 110 spaced around theentire circumference of the implant, the invention is not so limited. Byway of example only, one or more arms 110 may be truncated or omittedfrom a side or sides to limit the expansion of the width of the implant.A preferred embodiment of implant 100 would have at least two arms 110on each of upper and lower arcuate portions 106 a, 106 b, each of arms110 being adapted to be radially expanded in a direction away from themid-longitudinal axis of implant 100. To accommodate side-by-sideplacement of implants, arms 110 may be of different lengths. Implant 100preferably includes at least one external thread 122 to permit for therotational insertion of implant 100 into the disc space and betweenadjacent vertebral bodies a human spine. Although a preferred embodimentof the implant includes threads, the invention is not so limited. Forexample, the exterior of implant 100 may include other bone engagingsurfaces such as projections, splines, knurling, ratchets, or othersurface roughenings to resist expulsion of the implant from theimplantation space after implantation.

As shown in FIGS. 1-4, trailing end 102 preferably is configured tocooperatively engage a driver 300 shown in FIG. 12 used to installimplant 100 into the disc space. For example, trailing end 102 mayinclude truncated sides 124 for cooperatively engaging flanges 310 ofdriver 300 and recesses 126 a and 126 b for engaging pins 312 a and 312b, respectively, of driver 300. Trailing end 102 of implant 100 has anopening 128 sized for receiving a post 200 for engagement with radialexpander 120.

Post 200 is configured to be inserted into implant 100 through trailingend 102. Post 200 preferably has a shaft 202 with at least one thread204 and a head 206. Head 206 includes a tool engagement area 208 forcooperatively engaging a tool used for inserting and removing post 200from implant 100. Area 208 is shown as having a hex-shaped engagementsurface, but it is understood that area 208 may have any configurationsuitable for its intended purpose. The distal end of post 200 passesthrough opening 128 of implant 100 and extends into the interior ofimplant 100 to engage radial expander 120. Thread 204 is adapted tocooperatively engage radial expander 120 to move radial expander towardtrailing end 102 of implant 100 and force arms 110 apart to expandimplant 100. Shaft 202 may be at least in part smooth to permit movementof shaft 202 within opening 128 without engagement to opening 128.

As shown in FIGS. 6-8A, radial expander 120 is configured to be insertedat least in part within hollow interior 103 of implant 100. Expander 120preferably has a leading face 130 adapted to be oriented toward trailingend 102 of implant 100 and an opposite trailing face 132 adapted to beoriented toward leading end 104 of implant 100 when inserted withinhollow interior 103 of implant 100. A preferred radial expander 120 hasan opening 134, guide pegs 136, and a rim 138 adapted to bear againstinterior surface 114 of arms 110. Radial expander 120 is preferably atleast in part circular or may have any other configuration suitable forits intended purpose. Opening 134 is preferably threaded to cooperatewith thread 204 of post 200 to move radial expander 120 toward trailingend 102 of implant 100. Although threaded rotational engagement ispreferred for moving radial expander 120, the invention is not solimited. For example, post 200 may be configured to engage radialexpander 120 with a retractable flange or projection and pull expander120 into position to expand arms 110. Preferably, expander 120 has afixed shape.

Guide pegs 136 of radial expander 120 are adapted to fit within spaces112 such that as post 200 is rotated, radial expander 120 advances in alinear direction away from leading end 104 towards trailing end 102 ofimplant 100. Pegs 136 prevent substantial rotation of radial expander120 during rotation of post 200. Although two guide pegs 136 are shownextending from radial expander 120, the number and shape of pegs 136 maybe varied as suitable for their intended purpose.

FIG. 8B shows a radial expander 120′ incorporating two alternativeembodiments in accordance with the present invention. Radial expander120′ is adapted to selectively expand the height of implant 100 and tolimit or prevent the expansion of the width of implant 100. Theconfiguration of radial expander 120′ provides for the selectivemovement of one or more arms 110 away from the mid-longitudinal axis ofimplant 100 as radial expander 120′ is advanced into implant 100. Forexample, radial expander 120′ may have one or more truncated sides 135to form a reduced width portion of radial expander 120′. Truncated side135 is preferably configured to avoid contact with the interior surface114 of arms 110 adjacent truncated side 135 and is preferably configuredto clear interior surface projections such as, for example, ramp 116 ofarm 110 during the advancement of radial expander 120′ toward leadingend 102. Instead of truncated side 135, radial expander 120′ may includea groove 137 configured to receive at least a portion of an arm 110adjacent thereto. In its preferred use, at least the upper and lowerportions of rim 138 of radial expander 120′ bear against the interiorsurface 114 of arms 110 to expand the height of implant 100 so as not toinduce expansion of any arm or arms 110 adjacent truncated side 135 orgroove 137, as the case may be. The expansion of the implant may becontrolled by the interaction of the radial expander and arms of theimplant to expand the width to only one side or to expand both sides bydifferent amounts and involve one or more arms on a side of the implant.It is appreciated that other configurations of radial expander 120′ arepossible to achieve its intended purpose without departing from thescope of the present invention.

FIG. 9 shows implant 100 in a collapsed state. After insertion into thedisc space, post 200 is rotated, causing radial expander 120 to travelwithin the interior of implant 100 from a position proximate leading end104 toward trailing end 102. Pegs 136 travel within space 112 and cancontact the sides of arms 110 to limit rotation of radial expander 120during rotation of post 200.

FIG. 10 shows rim 138 of radial expander 120 moved along interiorsurface 114 of implant 100 after post 200 is initially rotated, andshows rim 138 in contact with ramp portions 116 of implant 100. Movementof radial expander 120 away from leading end 104 along ramp portions 116forces arms 110 to move away from the mid-longitudinal axis of implant100 and toward the adjacent vertebral bodies.

As shown in FIG. 11, continued rotation of post 200 causes radialexpander 120 to traverse ramp portions 116 and enter seat 118 of implant100. The entrance to seat 118 is narrower than the remainder of seat 118to prevent radial expander 120 from backing-out. Radial expander 120 isfurther held into place within seat 118 by arms 110. The sloped sides ofseat 118 form an inclined plane that inhibits movement of radialexpander 120 toward leading end 104 of implant 100. With radial expander120 seated in seat 118, arms 110 are forced apart at a greater distanceas measured from leading end 104 to the mid-longitudinal axis than fromtrailing end 102 to the mid-longitudinal axis to place implant 100 intoan expanded state. After implant 100 is in the expanded state, post 200can be removed from implant 100 by rotation in the opposite direction,and radial expander 120 remains in seat 118 to maintain the expandedheight and width of implant 100.

FIGS. 12-14 show an implant driver 300 for inserting implant 100 into adisc space. Implant driver 300 has a shaft 302, a distal end 304, and aproximal end 306. Shaft 302 is preferably hollow and is adapted topermit the passage of other instruments therethrough as described below.Distal end 304 includes an implant engaging head 308 with flanges 310,pins 312 a, 312 b, and an opening 314. Implant engaging head 308 issized and shaped to cooperatively engage an implant to hold andmanipulate the implant during insertion into the disc space. Proximalend 306 includes a handle 316 for rotational and linear advancement ofdriver 300. Proximal end 306 preferably has a funnel-shaped opening 318passing through shaft 302 and expanding through distal end 304.Funnel-shaped opening 318 is preferably configured as shown in FIG. 14to facilitate the introduction of bone growth promoting material intoshaft 302. Funnel-shaped opening 318 is preferably sized and shaped toreceive other instruments therethrough, such as plunger 500 described inassociation with FIGS. 16 and 17 below.

FIG. 15 shows a rotating tool 400 for engaging and rotating post 200.Rotating tool 400 has a distal end 402 and a proximal end 404. Distalend 402 has a tip 406 adapted to cooperatively engage area 208 of post200. In a preferred embodiment, tip 406 is hex-shaped, but may be of anyshape suitable to engage post 200. Tip 406 is preferably adapted toengage area 208 of post 200 such that upon the disengagement of post 200from implant 100, rotating tool 400 can withdraw post 200 through shaft302 of driver 300. In order to facilitate the removal of post 200 suchthat post 200 and rotating tool 400 may be removed together, tip 406 maybe adapted to cooperatively engage with area 208, for example, via aninterference fit, detent, or retractable spring flange. Proximal end 404is preferably configured to engage a handle and has a stop 408. Proximalend 404 is preferably adapted to engage with a mechanical or manualdevice for rotating shaft 410.

FIGS. 16 and 17 show a plunger instrument for inserting bone growthpromoting material into implant 100 and into the surrounding disc space.Plunger 500 preferably has an outer shaft 502, an inner rod 504, and ahandle 506. Inner rod 504 preferably has a proximal end configured toengage a handle, such as a T-handle for example, and a stop 508 forlimiting the travel of inner rod 504 when placed within outer shaft 502.In use, plunger 500 may be inserted into an instrument adapted todeliver bone growth promoting material into implant 100 such as driver300. Plunger 500 and driver 300 together may be placed within a guardsuch as guard 600 of FIG. 18 to introduce bone growth promoting materialinto hollow interior 103 of implant 100 and preferably the disc spacesurrounding the implant.

In a preferred embodiment, bone growth promoting material is introducedinto hollow interior 103 of shaft 302 of driver 300 throughfunnel-shaped opening 318. Plunger 500 with inner rod 504 insertedtherein, may be inserted into the interior of driver 300 to push bonegrowth promoting material therethrough and into the implant. Plunger 500and inner rod 504 may further move bone growth promoting material intothe remaining areas inside and around the implant not yet filled withbone growth promoting material.

Plunger 500 preferably has a clamp 510 and stop 508 to limit theextension of inner rod 504 from outer shaft 502. Stop 508 may have anyconfiguration adapted to limit the travel of inner rod 504, for example,a shoulder, flange, or other projection. Although it is preferred thatinner rod 504 is solid, the invention is not so limited. Clamp 510 inthe tightened position holds inner rod 504 in fixed relationship toouter shaft 502 and preferably so as not to extend from the distal endof shaft 502. When clamp 510 is released, inner rod 504 is permitted totravel beyond the distal end of outer shaft 502 to the extent limited bystop 508.

FIGS. 18-30 show various steps of a preferred method for insertingimplant 100 and using associated instrumentation disclosed herein.

FIG. 18 is a perspective view of a segment of a spine viewed from aposterior aspect with the dural sac retracted to the left showing that apartial discectomy has already been performed. Guard 600, with discpenetrating extensions 602, 604 and window 606, is shown approaching thedisc space between the adjacent vertebral bodies with disc penetratingextensions 602, 604 in a first or insertion position.

It is appreciated that various types of guards may be used to provideprotected access to the disc space including, but not limited to, thosetaught by Michelson in application Ser. Nos. 10/085,731 and 10/085,406;and U.S. Pat. Nos. 5,015,247; 5,484,437; 6,080,155; and 6,210,412 all ofwhich are incorporated herein by reference.

An impaction cap 608 is positioned on the proximal end of guard 600 tomaintain it in the open position such that the disc penetratingextensions are closed into the insertion position. In this position,guard 600 is ready to be placed or driven into the disc space betweenthe adjacent vertebral bodies.

In FIG. 19, the extensions of guard 600 are fully inserted into thespine with the disc penetrating extensions parallel to one another inthe insertion position. Impaction cap 608 is shown holding the guard inthe open position and the disc penetrating extension in the insertionposition. Guard 600 rotationally articulates to permit movement of discpenetrating extensions 602, 604 in response to movement of a firstportion 610 and a second portion 612 relative to one another. Therotational articulation preferably occurs about a hinge 614, which ispreferably formed in first and second portions 610, 612.

In FIG. 20, guard 600 is shown in a closed position with the discpenetrating extensions shown in the inserted position to induce lordosisto the vertebral bodies. After closing guard 600, the proximal end has alock collar 616 placed around it to maintain guard 600 in the closedposition.

In FIG. 21, guard 600 is in a closed position with disc penetratingextensions 602, 604 in the inserted position to induce angulation to theadjacent vertebral bodies. At the distal end of guard 600 shown incross-section is a side view of a bone removal device such as a drill700 being inserted through guard 600. It is appreciated that other boneremoval devices suitable for the intended purpose such as, but notlimited to, burrs, reamers, mills, saws, trephines, chisels, and thelike may also be used and would be within the scope of the presentinvention. Guard 600 provides protected access to the disc space and theadjacent vertebral bodies for drill 700 via the elongated opening inguard 600.

Drill 700 may have a reduced diameter-cutting portion relative to theshaft diameter of guard 600 or may be inserted through an inner sleevethat passes into guard 600 to guide drill 700 to form an implantationspace smaller than the passage through guard 600. Thus, the guardopening may be taller than the height of the cutting portion of drill700. Such a taller opening also allows the implantation of an implanttaller than the height of the cutting portion of drill 700.

As best shown in FIG. 22, implant 100 and implant driver 300 may bepassed through guard 600 to insert implant 100 in a collapsed positioninto the disc space between the adjacent vertebral bodies. The guard maybe left in place throughout the procedure. Implant 100 is assembled withpost 200 inserted through trailing end 102 of implant 100 to engageradial expander 120 inserted in the collapsed position into hollowinterior 103 of implant 100 through leading end 104. Radial expander 120in this position may bear against the interior surface 114 of arms 110but does not yet force arms 110 apart so that implant 100 is in anon-expanded state. Implant 100 is preferably rotated into the discspace such that thread 122 penetrably engages the bone of the adjacentvertebral bodies.

As illustrated in FIG. 23, after implant 100 is installed in the desiredposition in the implantation space between the adjacent vertebral bodieswith opposed arcuate portions 106 a and 106 b oriented toward theadjacent vertebral bodies, rotating tool 400 is used to engage androtate post 200 so as to pull radial expander 120 away from leading end104 and toward trailing end 102 along the interior surface 114 of arms110 to transition implant 100 from a collapsed position to an expandedposition.

As shown in FIG. 24, as rotating tool 400 is rotated, radial expander120 moves toward trailing end 102 of implant 100 causing arms 110 tomove radially outward away from the mid-longitudinal axis of implant100. The interaction between radial expander 120 and arms 110 is bestshown in FIGS. 9-11. The radial expansion of implant 100 results in agreater implant height and width proximate leading end 104 than theimplant height and width proximate trailing end 102. Upper and lowerarcuate portions 106 a, 106 b are positioned in angular relationship toeach other and position the vertebral bodies adjacent implant 100 in anangular relationship to each other.

As shown in FIGS. 25 and 25A, after implant 100 is in the expandedstate, post 200 is removed by rotating tool 400 from implant 100.Rotating tool 400 is adapted to cooperatively engage tool engagementarea 208 of post 200. The leading end of rotating tool 400 may betapered to allow the tip of tool 400 to slightly bind and positivelyengage tool engagement area 208. Radial expander 120 remains seatedwithin hollow interior 103 of implant 100 to hold arms 110 in a radiallyexpanded state.

FIGS. 26 and 27 show a preferred method for insertion of bone growthpromoting materials into implant 100 and the disc space surroundingimplant 100. Driver 300 is shown inserted into guard 600 with its distalend adjacent to and in communication with opening 128 of implant 100 toaccess hollow interior 103 of implant 100. Bone growth material isintroduced into funnel shaped end 318 of driver 300. Plunger 500 withinner rod 504 in the retracted position is used to push and load thebone growth promoting material through shaft 302 of driver 300 and intoimplant 100. Sufficient bone growth promoting material is introducedinto driver 300 to at least partially fill implant 100. Alternatively,the implant may be pre-loaded with bone growth promoting material priorto its insertion into the implantation space. Additional bone growthmaterial may be added to fill any space within the implant created as aresult of transitioning implant 100 to an expanded position as describedbelow.

As shown in FIG. 27, after the implant is at least partially filled withbone growth promoting material, inner rod 504 is moved forward in theextended position into implant 100 through opening 128 of trailing end102 to push the bone growth promoting material in its path throughopening 134 of radial expander 120. Distributing bone growth promotingmaterial beyond radial expander 120 fills the interior of implant 100proximate leading end 104 and introduces bone growth promoting materialfurther into the disc space beyond leading end 104 and unoccupied byimplant 100. After inner rod 504 is retracted from within the interiorof implant 100 and plunger 500 is removed from driver 300, additionalbone growth promoting material may be inserted into driver 300. Plunger500 then may be used to fill the space left unoccupied by the removal ofinner rod 504 with bone growth promoting material and further pack bonegrowth promoting material into implant 100. After filling implant 100and the surrounding disc space with bone growth promoting material,plunger 500 and driver 300 are removed from guard 600. The trailing endof guard 600 is then opened to return disc penetrating extensions 602,604 to the closed position to facilitate the removal of guard 600 fromthe disc space.

FIGS. 28-32 show a preferred remover and methods of disengaging radialexpander 120 from seat 118 of implant 100 if it is desired to uninstallimplant 100 or other implants of the present invention designed for agenerally posterior insertion. FIG. 28 shows post 200 being partiallythreaded into a seated radial expander 120 by rotating tool 400 suchthat a portion of post 200 extends from trailing end 102 of implant 100.As shown in FIG. 29, post 200 may then be advanced in a linear directionwithout substantial rotation toward leading end 104 of implant 100 suchas, for example, with an impaction force. The linear advancement of post200 toward leading end 104 moves expander 120 out of seat 118 and towardleading end 104. This allows the implant arms to collapse inward to theunexpanded state, thereafter allowing the implant to be unthreaded orotherwise removed from the spine. The implant holder may be attachedprior to collapsing the implant or thereafter. With expander 120 removedfrom the interior of implant 100, arms 110 are no longer held in aradially expanded position, thereby causing implant 100 to collapse toan unexpanded state.

With reference to FIGS. 30-32, in certain circumstances, for example,where it may be desirable to revise an instrumentation and to accessimplant 100 from an anterior aspect of the spine, radial expander 120may be removed from the leading end 104 (oriented near the anterioraspect of the space) of implant 100. FIG. 30 shows a remover 800 forremoving radial expander 120 from hollow interior 103 of implant 100through leading end 104. Remover 800 has a shaft 802, a distal end 804,and a proximal end 806. Distal end 804 has a threaded rod 808 and anenlarged head 810 with a diameter configured to enter hollow interior103 of implant 100 in a radially expanded state and force apart arms110. Proximal end 806 is preferably configured to be attached to aremovable handle for rotating remover 800.

Threaded rod 808 of remover 800 threads into radial expander 120 causingforward movement of remover 800 toward leading end 104 of implant 100.As remover 800 moves toward leading end 104, enlarged head 810 contactsinterior surface 114 of arms 110, forcing arms 110 to move outward andfurther away from the mid-longitudinal axis of implant 100. Thismovement in turn causes seat 118 to expand outward opening the entranceto seat 118, thus permitting radial expander 120 to be removed from seat118 of implant 100. FIG. 32 shows remover 800 removing radial expander120 from seat 118 to return arms 110 to their initial non-expandedposition. The implant may then be removed from the implantation site ifdesired.

The method of the present invention may also be performed from ananterior approach to the spine. FIGS. 33-56 show various embodiments ofan implant 900 for insertion from at least in part an anterior approachto the spine as well as instruments and the associated method forinserting and removing implant 900. Implant 900 is similar to implant100, with certain differences noted below. As shown in FIGS. 33-36,implant 900 has an open trailing end 902, a leading end 904 shown closedin this embodiment, a base 905 proximate the leading end, and ashortened arm 909 and lengthened arms 910 extending from base 905. FIG.37 shows an alternative embodiment of implant 900 having two opposedshortened arms 909 and lengthened arms 910. Shortened arms 909 arepreferably located on at least one side of implant 900 when two implantsare inserted side-by-side as shown in FIGS. 52A, 52B, and 53. Shortenedarms 909 provide for a reduced diameter of trailing end 902 such thattrailing end 902 does not substantially protrude from the disc space tominimize the risk of interference with delicate vascular andneurological structures present adjacent to the disc space. Shortenedarms 909 also permit two implants 900 in an expanded state to be placedside-by-side in close proximity to each other in the disc space.Although a combination of shortened arms 909 and lengthened arms 910 ispreferred, the invention is not so limited. For example, in situationswhere the surgeon determines it is appropriate, implant 900 may havearms 910 of generally equal length as shown in another alternativeembodiment of implant 900 in FIG. 38.

The interaction between radial expander 920 and the interior surface ofarms 909, 910 is similar to that between radial expander 120 and arms110 (described in relation to FIGS. 9-11) except that unlike theinterior surface of arm 110, shortened arms 909 have a notched area 917that functions to hold the radial expander 920 in seat 918 and maintainshortened arms 909 in a radially expanded state when radial expander 920is seated in seats 918 of lengthened arms 910.

In implant 900 a post 1000 is inserted through the trailing end 902.Leading end 904 preferably has a threaded opening 928 for threadablyengaging post 1000. Post 1000 has a shaft 1002 with a first thread 1004for cooperative engagement with a tool 1300 shown in FIG. 44 for pushingor otherwise moving radial expander 920 away from trailing end 902 andtoward base 905 proximate leading end 904 of implant 900. Post 1000 hasa head 1006 with a tool engagement area 1008 that is preferablyhex-shaped to engage a post remover 1400 shown in FIG. 45, and a secondthread 1010 shown in FIGS. 50, 51 at the end opposite head 1006 forcooperative engagement with threaded opening 928 in leading end 904 ofimplant 900.

As an alternative to using a post with a threaded end for engagementwith the leading end of the implant, a post may be used having a leadingend with a retractable flange or other projection for cooperativeengagement with the leading end of the implant. Such a post may then beused to rotate the radial expander into position in a fashion similar tothat described with reference to FIGS. 23 and 24. Once the radialexpander is seated, the flanges or other projections may be retracted,and the post may then be withdrawn.

As shown in FIGS. 33 and 39-41, radial expander 920 is similar to radialexpander 120 shown in FIGS. 6-8. Opening 934 of radial expander 920 ispreferably unthreaded. A threaded opening is not essential since radialexpander 920 is moved by rotating tool 1300 and not by post 1000,described in more detail below.

FIG. 42 shows an implant driver 1100 for inserting implant 900 into adisc space. Driver 1100 has a shaft 1102 and a distal end 1104. Distalend 1104 preferably has an implant engaging head 1108 with flanges 1110spaced apart by recessed areas and a bore 1120. Implant engaging head1108 is preferably sized and shaped to cooperatively engage trailing end902 of implant 900 for insertion into the disc space. Implant engaginghead 1108 preferably is tapered to facilitate insertion into theinterior of implant 900 and to facilitate the placement of flanges 1110into spaces 912. Arms 909, 910 fit into recessed areas between flanges1110. In this position, driver 1100 is engaged to implant 900 and canrotate implant 900. Bore 1120 is preferably configured to receive post1000 so that driver 1100 may insert implant 900 with post 1000 alreadyattached thereto.

FIG. 43 shows an implant holder 1200 for holding implant 900 in a stableposition while one or more tools, for example rotating tool 1300,engages with post 1000 to move radial expander 920 toward leading end904. Implant holder 1200 has a distal end 1202, a proximal end 1204, ashaft 1206 therebetween, and a handle 1208. Distal end 1202 preferablyhas a plurality of flanges 1210 that are configured for engagement withspaces 912 between arms 909, 910. Shaft 1206 is preferably hollow andsized to accommodate the passage of tools therethrough, for example,rotating tool 1300. Flanges 1210 are adapted to fit in spaces 912between arms 909, 910 to hold implant 900. Rotating tool 1300 is used torotate post 1000 to move radial expander 920 while implant 900 is heldstable by holder 1200 to resist the rotational forces bearing upon post1000.

FIG. 44 shows rotating tool 1300 for advancing radial expander 920 awayfrom trailing end 902 and toward base 905 proximate leading end 904.Rotating tool 1300 has a distal end 1302 and a shaft 1310. Distal end1302 has a bore 1312 with a thread 1314 adapted to cooperatively engagewith first thread 1004 of post 1000. Bore 1312 preferably has anunthreaded portion at its leading end that permits rotating tool 1300 tomove over a portion of post 1000 such as post head 1006 prior toengagement of the thread. As tool 1300 is rotated onto post 1000, distalend 1302 bears against radial expander 920 to advance radial expander920 into implant 900. After radial expander 920 is seated into seat 918,rotating tool 1300 is unthreaded from post 1000 and removed from implant900.

FIG. 45 shows a post remover 1400 for removing post 1000 after radialexpander 920 has been seated in seat 918 of implant 900. Post remover1400 has a shaft 1402 and a distal end 1404. Distal end 1404 has a bore1406 with a post engagement surface 1408 that is preferably hex-shapedto cooperatively engage with tool engagement area 1008 of post 1000.Post remover 1400 removes post 1000 from implant 900 by unthreading post1000 from opening 928 in leading end 904 of implant 900.

FIGS. 46-51 show various steps of a preferred method for insertingimplant 900 from an anterior approach to the spine and using associatedinstrumentation disclosed herein.

FIGS. 46 and 47 show insertion of a guard 1600 with disc penetratingextensions 1602 into the disc space and the use of drill 700 to preparethe disc space for implantation. Disc penetrating extensions 1602 neednot be but are preferably angled to place the adjacent vertebral bodiesin angular relationship to each other. As taught in U.S. Pat. No.6,080,155 to Michelson incorporated by reference herein, the guard mayhave one or more extensions of any size or shape suitable for theintended purpose and one or more bores which could, but need not, be inpart overlapping. It is understood that the use of such a guard is onlypreferred and not required. The guard may be of any type suitable forthe purpose of providing protected access while the disc space isprepared and during implantation including, but not limited to, theguards incorporated by reference above.

In FIG. 48, drill 700 and guard 1600 are withdrawn and driver 1100 isused to insert implant 900 into the prepared disc space. In thisexample, implant 900 is rotatably inserted so that thread 922 penetrablyengages the bone of the adjacent vertebral bodies. At the option of thesurgeon, guard 1600 may be left in place throughout the whole procedure,the procedure then being carried out through the hollow shaft of guard1600. Additionally, implant 900 may be installed without firstinstalling post 1000 into implant 900. However, it is preferred thatpost 1000 is installed in implant 900 before implant 900 is installedinto the disc space.

As illustrated in FIG. 49, radial expander 920 is moved onto post 1000and implant holder 1200 is moved into position. After flanges 1210 ofimplant holder 1200 are engaged with arms 909, 910 of implant 900,rotating tool 1300 is inserted through the interior of shaft 1206 sothat threaded bore 1302 of rotating tool 1300 cooperatively engagesfirst thread 1004 of post 1000. As shown in FIG. 50, after rotating tool1300 and post 1000 are rotationally engaged, continued rotation ofrotating tool 1300 linearly forces radial expander 920 away fromtrailing end 902 and to bear against the interior surfaces of arms 909,910, causing arms 909, 910 to be forced away from the mid-longitudinalaxis of the implant as described above in relation to implant 100 andFIGS. 9-11.

As shown in FIG. 51, after radial expander 920 is seated into seat 918and implant 900 is placed in an expanded state, post remover 1400 isused to engage head 1006 of post 1000. Rotating post remover 1400disengages post 1000 from threaded opening 928 of implant 900, allowingpost 1000 to be withdrawn through opening 934 of radial expander 920 andfrom the interior of the implant.

FIGS. 52A, 52B, and 53 show two implants 900 in a radially expandedstate placed in close proximity to one another within the perimeter of adisc space D. In FIG. 52A and 52B, implants 900 of FIG. 33 arepreferably positioned such that shortened arms 909 face theantero-lateral aspect of the vertebral bodies such that the structure ofeach implant is kept substantially within the disc space to minimize therisk of interference with delicate vascular and neurological structurespresent adjacent to the disc space. In FIG. 52B, implants 900 areoriented toward each other in a toed-in configuration permitting theimplants to be closer to each other in a side-by-side placement. Suchplacement permits the use of larger implants to better fill the discspace than may be possible with implants positioned parallel to eachother.

In FIG. 53, two implants 900 of FIG. 37, each having opposed shortenedarms 909, are preferably placed such that the mid-longitudinal axis ofeach implant are in closer proximity to one another than the embodimentshown in FIG. 52A. Closer placement is made possible, by way of exampleonly, by positioning each implant such that shortened arms 909 face eachother within the disc space. Additionally, the size of thread 922 may bereduced towards trailing end 902 so that trailing end 902 has a reducedthread portion 923 to minimize contact with the thread of an adjacentimplant. Such an orientation permits greater expansion to occur withouta lengthened arm from one implant crossing the lengthened arm of animplant adjacent thereto. In all the embodiments described herein, itshould be apparent that a number of arrangements of shortened and/orlengthened arms are possible and all within the broad scope of thepresent invention.

FIGS. 54-56 show a preferred remover and methods of disengaging radialexpander 920 from seat 918 of implant 900 if it is desired to uninstallimplant 900. FIG. 54 shows a remover 1500 for removing radial expander920 from hollow interior 903 of implant 900 through trailing end 902.Remover 1500 has a shaft 1502 and a distal end 1504. Distal end 1504 hasa bore 1514 with a thread 1516 that is configured for cooperativeengagement with first thread 1004 of post 1000, a collar 1518 with anouter diameter slightly smaller than the diameter of hollow interior 903of implant 900 in a radially expanded state, and a bearing 1520 thatallows remover 1500 to rotate relative to collar 1518. Bore 1514preferably has an unthreaded portion at its leading end that permitsremover 1500 to move over a portion of post 1000 prior to rotationalengagement.

As shown in FIGS. 55 and 56, threaded bore 1514 of remover 1500 threadsonto post 1000 causing forward movement of remover 1500 into trailingend 904 of implant 900. As remover 1500 moves into trailing end 904,collar 1518 contacts arms 909, 910, forcing arms 909, 910 to moveoutward away from the mid-longitudinal axis of the implant. Thismovement in turn causes seat 918 to expand outward to release radialexpander 920, thus permitting radial expander 920 to be removed fromimplant 900.

FIG. 56 shows an instrument, for example a hook 1700, for removingradial expander 920 from implant 900 to return arms 909, 910 to theirinitial or non-expanded position.

The implants described herein preferably have a generally circular crosssection transverse to the mid-longitudinal axis of the implant. In thecollapsed position, the implants may have a generally cylindricalconfiguration or may be in the shape of a cylinder with at least aportion of a side removed. The implants may be tapered from trailing endto leading end and may have a generally frusto-conical configuration inthe collapsed position to facilitate insertion into the implantationspace.

In another embodiment, in the expanded position, the implants describedherein may have a leading end or a trailing end tapered at an angle thatmatches the angle of the upper, lower, and side portions in the expandedposition.

The radially expandable spinal fusion implant may include, be made of,treated, coated, filled, used in combination with, or have a hollow forcontaining artificial or naturally occurring materials and/or substancessuitable for implantation in the human spine. These materials and/orsubstances include any source of osteogenesis, bone growth promotingmaterials, bone, bone derived substances or products, demineralized bonematrix, ossifying proteins, bone morphogenetic proteins, hydroxyapatite,genes coding for the production of bone, and bone including, but notlimited to, cortical bone. The implant can also be formed of anartificial material stronger than bone such as metal including, but notlimited to, titanium and its alloys, surgical grade plastics, plasticcomposites, ceramics, or other materials suitable for use as a spinalfusion implant. The implant can include at least in part of materialsthat are bioabsorbable and/or resorbable in the body such as bone and/orbone growth promoting materials. The implant of the present inventioncan be formed of a porous material or can be formed of a material thatintrinsically participates in the growth of bone from one of adjacentvertebral bodies to the other of adjacent vertebral bodies. Where suchimplants are for posterior implantation, the trailing ends of suchimplants may be treated with, coated with, or used in combination withchemical substances to inhibit scar tissue formation in the spinalcanal. The implants of the present invention may be adapted tofacilitate the electrostimulation of the fusion area into which they areinserted and the proximate bone thereabout. The implant of the presentinvention may be modified, or used in combination with materials to makeit antibacterial, such as, but not limited to, electroplating or plasmaspraying with silver ions or other substance. At least a portion of theimplant may be treated to promote bone ingrowth between the implant andthe adjacent vertebral bodies. The implant of the present invention maybe used in combination with spinal fixation hardware, bone screws,plates, rods, tethers of synthetic chords or wires.

Although various embodiments of the present invention have beendisclosed, they are but preferred embodiments for the purpose ofillustration by example and not limitation. It should be understood thatany modifications of these teachings as would be known to one ofordinary skill in the art are anticipated and within the scope of thepresent inventive teachings.

1. An orthopedic implant for implantation at least in part between twoadjacent bone masses, said implant comprising: a body having a leadingend, a trailing end opposite said leading end, a mid-longitudinal axis,and a length between said leading and trailing ends of said body, saidbody having a mid-point bisecting the length of said body, said bodyhaving a first side portion adapted to contact one of the adjacent bonemasses, a second side portion opposite said first side portion adaptedto contact another one of the adjacent bone masses, and at least a thirdside portion between said first and second side portions, each of saidfirst, second, and third side portions extending from said trailing endof said body and being spaced apart from one another to form a hollowinterior therebetween, said hollow interior being configured to hold atleast some bone growth promoting material therein, each of said first,second, and third side portions configured to move at least in part in adirection away from the mid-longitudinal axis of the body allowing forexpansion of said body in at least three directions, said first, second,and third side portions having a collapsed position and an expandedposition; and an expander at least in part within said hollow interior,said expander configured to cooperatively engage an instrument adaptedto be inserted through said trailing end of said body to engage and tomove said expander from a position proximate said leading end when saidbody is in the collapsed position away from said leading end and towardsaid trailing end of said body to place said body in the expandedposition, said, expander adapted, to contact and to move said first,second, and third side portions away from the mid-longitudinal axis ofsaid body, said first, second, and third side portions of said bodyadapted to cooperatively engage said expander to locate said expander ata fixed position along the length of said body, said fixed positionbeing closer to the mid-point of said implant than to said leading endof said implant, said first, second, and third side portions of saidbody adapted to resist dislodgment of said expander from that locationwhen said implant is in the expanded position, said expander adapted tohold at least a portion of said first, second, and third side portionsapart so as to maintain the expanded position of said body and to resistthe collapse of said body to the collapsed position when said body is inthe expanded position, when said body is in the expanded position saidhollow interior being substantially unobstructed by any mechanism tomove said expander so as to permit growth of bone through a portion ofsaid hollow interior between said expander and said trailing end andthrough a portion of said hollow interior between said expander and saidleading end of said body.
 2. The implant of claim 1, wherein saidexpander includes a threaded opening for threadable engagement with saidinstrument used to move said expander from an initial position to afinal position to place said body in the expanded position.
 3. Theimplant of claim 1, wherein each of said first, second, and third sideportions are configured to permit said expander to seat therein in atleast said expanded position.
 4. The implant of claim 1, wherein atleast a portion of said first, second, and third side portions areseparated by a space, said expander includes at least one guide pegextending therefrom and configured to be placed in said space between atleast a portion of at least one of said first, second, and third sideportions.
 5. The implant of claim 1, wherein at least one of said first,second, and third side portions comprises a plurality of arms separatedfrom one another at least in part by a space, said space being at leastone of an opening, slit, and slot.
 6. The implant of claim 5, whereinsaid arms are of different lengths.
 7. The implant of claim 5, whereinsaid arms are aligned parallel with the mid-longitudinal axis of saidbody in the collapsed position.
 8. The implant of claim 1, wherein atleast one of said first, second, and third side portions has an interiorsurface, at least a portion of said interior surface forming a rampadapted to contact said expander.
 9. The implant of claim 1, wherein atleast one of said first, second, and third side portions has an interiorsurface, at least a portion of said interior surface forming a seatadapted to receive and locate said expander along the length of saidbody.
 10. The implant of claim 1, wherein at least one of said first,second, and third side portions is sufficiently resilient so as to bendto be moved away from said mid-longitudinal axis of said body.
 11. Theimplant of claim 1, wherein said first, second, and third side portionswhen said implant is in the collapsed position form a generallycylindrical shape.
 12. The implant of claim 1, further in combinationwith said instrument, said instrument including a post adapted to beinserted at least in part within said hollow interior of said body formoving said expander along at least a portion of the length of said bodybetween said first and second side portions of said implant, said posthaving a shaft with a first end adapted to be coupled to one of saidleading and trailing ends of said body and a second end opposite saidfirst end configured to cooperatively engage a tool used for insertingsaid post into said body.
 13. The implant of claim 12, wherein saidshaft is at least in part threaded and said expander has a threadedopening configured to threadably engage said shaft so that rotation ofsaid post within said body moves said expander along at least a portionof the length of said body to force apart said first, second, and thirdside portions.
 14. The implant of claim 13, wherein said threaded partof said shaft of said post extends a distance greater along said shaftthan the depth of said threaded opening of said expander.
 15. Theimplant of claim 1, wherein said trailing end of said body includes atleast one non-threaded opening.
 16. The implant of claim 1, furthercomprising a bone engaging surface formed on the exterior of at leastsaid first, second, and third side portions for engaging the adjacentbone masses, said bone engaging surface including at least one of athread, a ratchet, a spline, surface roughenings, and knurling.
 17. Theimplant of claim 1, wherein said implant comprises an artificialmaterial other than bone.
 18. The implant of claim 1, further comprisinga thread formed on the exterior of at least said first, second, andthird side portions for engaging the adjacent bone masses, said threadextending continuously around the mid-longitudinal axis of said implantfor at least one complete turn.
 19. The implant of claim 1, wherein saidtrailing end of said implant has a constant cross section transverse tothe mid-longitudinal axis in both the collapsed and expanded positions.20. The implant of claim 1, wherein each of said first, second, andthird side portions has a free end at said leading end of said implant.21. An orthopedic implant for implantation at least in part between twoadjacent bone masses, said implant comprising: a body having a leadingend, a trailing end opposite said leading end, a mid-longitudinal axis,and a length between said leading and trailing ends of said body, saidbody having a mid-point bisecting the length of said body, said bodyhaving a first side portion adapted to contact one of the adjacent bonemasses, a second side portion opposite said first side portion adaptedto contact another one of the adjacent bone masses, and at least a thirdside portion between said first and second side portions, each of saidfirst, second, and third side portions extending from said trailing endof said body and being spaced apart from one another to form a hollowinterior therebetween, each of said first, second, and third sideportions configured to move at least in part in a direction away fromthe mid-longitudinal axis of the body allowing for expansion of saidbody in at least three directions, said first, second, and third sideportions having a collapsed position and an expanded position; anexpander at least in part within said hollow interior, said expanderconfigured to cooperatively engage an instrument adapted to be insertedthrough said trailing end of said body to engage and to move saidexpander from a position proximate said leading end when said body is inthe collapsed position away from said leading end and toward saidtrailing end of said body to place said body in the expanded position,said expander adapted to contact and to move said first, second, andthird side portions away from the mid-longitudinal axis of said body,said first, second, and third side portions of said body adapted tocooperatively engage said expander to locate said expander at a fixedposition along the length of said body, said fixed position being closerto the mid-point of said implant than to said leading end of saidimplant, said first, second, and third side portions of said bodyadapted to resist dislodgment of said expander from that location whensaid implant is in the expanded position, said expander adapted to holdat least a portion of said first, second, and third side portions apartso as to maintain the expanded position of said body and to resist thecollapse of said body to the collapsed position when said body is in theexpanded position; and a bone growth promoting material, said hollowinterior being configured to hold at least some of the bone growthpromoting material therein.
 22. The implant of claim 21, wherein saidbone growth promoting material is selected from one of bone, bonederived products, demineralized bone matrix, ossifying proteins, bonemorphogenetic protein, hydroxyapatite, and genes coding for theproduction of bone.
 23. An orthopedic implant for implantation at leastin part between two adjacent bone masses, said implant comprising: abody having a leading end, a trailing end opposite said leading end, amid-longitudinal axis, and a length between said leading and trailingends of said body, said body having a mid-point bisecting the length ofsaid body, said body having a first side portion adapted to contact oneof the adjacent bone masses, a second side portion opposite said firstside portion adapted to contact another one of the adjacent bone masses,and at least a third side portion between said first and second sideportions, each of said first, second, and third side portions extendingfrom said trailing end of said body and being spaced apart from oneanother to form a hollow interior therebetween, said hollow interiorbeing configured to hold at least some bone growth promoting materialtherein, each of said first, second, and third side portions configuredto move at least in part in a direction away from the mid-longitudinalaxis of the body allowing for expansion of said body in at least threedirections, said first, second, and third side portions having acollapsed position and an expanded position; and an expander at least inpart within said hollow interior, said expander configured tocooperatively engage an instrument adapted to be inserted through saidtrailing end of said body to engage and to move said expander from aposition proximate said leading end when said body is; in the collapsedposition away from said leading end and toward said trailing end of saidbody to place said body in the expanded position, said expander adaptedto contact and to move said first, second, and third side portions awayfrom the mid-longitudinal axis of said body, said first, second, andthird side portions of said body adapted to cooperatively engage saidexpander to locate said expander at a fixed position along the length ofsaid body, said fixed position being closer to the mid-point of saidimplant than to said leading end of said implant, said first, second,and third side portions of said body adapted to resist dislodgment ofsaid expander from that location when said implant is in the expandedposition, said expander adapted to hold at least a portion of saidfirst, second, and third side portions apart so as to maintain theexpanded position of said body and to resist the collapse of said bodyto the collapsed position when said body is in the expanded position,wherein said implant is at least in part resorbable.